Two cars carrying LPG and one empty car left the tracks, which are owned by Canadian National Railway, at around 7:30 a.m. local time (1230 GMT) said Amy McBeth, spokeswoman for BNSF. BNSF is owned by Berkshire Hathaway.

There were no leaks detected, or injuries or fire due to the accident.

The RCMP had said earlier that two cars carrying unscented propane had derailed.

Emerson, located near the U.S. border, is 110 km (68 miles) south of Winnipeg, Canada's rail network hub.

The derailment comes at a time of increased regulatory scrutiny on the railroads, as Canada and the United States ramp up efforts to increase rail car safety after a series of fiery accidents involving trains carrying crude oil.

An RCMP spokeswoman said it was unclear when residents would be able to return to their homes, or what had caused the derailment.

BNSF's McBeth said crews were working to clear the tracks but she had no estimate of how long it would take.

"At this point it's too early to know what caused the derailment, but we will certainly be conducting a full investigation," she said. (Editing by Marguerita Choy and Jonathan Oatis)